#include<stdio.h>
int main(int argc, char const *argv[])
{   
    //mm转mil
    double _mil , _mm;
    printf("请输入一个mm数 \n");
    scanf("%lf" , &_mm);
    _mil = 0.0254 * _mm;
    printf("%lf mm等于 %lf mil \n",_mm , _mil);

    //mil转mm
    printf("请输入一个mil数 \n");
    scanf("%lf" , &_mil);
    _mm = _mil/0.0254;
    printf("%lf mil等于 %lf mm \n",_mil,_mm);
    return 0;
}
